Servo pattern architecture and method using same to improve LPOS encoding efficiency

ABSTRACT

A sequential data storage medium, such as for example and without limitation a magnetic tape, comprising a sequence of plurality of servo patterns encoded therein, which provide lateral position information and LPOS information. Each servo pattern comprises a first burst comprising a first pulse, a second pulse, a third pulse, a fourth pulse and a fifth pulse and a second burst comprising a sixth pulse, a seventh pulse, an eighth pulse, a ninth pulse and a tenth pulse. The widths of the plurality of pulses, in combination with the spacings between the plurality of pulses, encode two bits of data.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation Application claiming priority from aU.S. Utility Application having Ser. No. 12/143,094 filed Jun. 5, 2008,the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

Applicant's invention relates to servo pattern architecture, and amethod using that servo pattern architecture, to improve linear position(“LPOS”) encoding efficiency in a sequential storage medium, such as forexample a magnetic tape.

BACKGROUND OF THE INVENTION

Timing-based servo (TBS) is a technology developed for linear tapedrives. In TBS systems, recorded servo patterns consist of transitionswith two different azimuthal slopes. Head position is derived from therelative timing of pulses, or dibits, generated by a narrow head readingthe relatively wide servo patterns. TBS patterns also allow the encodingof additional longitudinal position (LPOS) information without affectingthe generation of the transversal position error signal (PES). This isobtained by shifting transitions from their nominal pattern positionusing pulse-position modulation (PPM).

A specification for the servo format in current midrange tape drives isprovided by the linear tape-open (LTO) format. The complete format forLTO drives of generation 1 (LTO-1) was standardized by the EuropeanComputer Manufacturers Association (ECMA) in 2001 as ECMA-319.

Traditionally, the detection of LPOS information bits is based on theobservation of the shifts of the arrival times of the dibit peaks withinthe servo bursts at the servo reader output. It is known in the art toencode by pulse position modulation an LPOS word comprising 36 bits ofinformation in a non-data region of a sequential data storage medium,such as a magnetic tape. Each encoded LPOS word in the standard ECMA-319on data interchange on 12.7 mm 384-track magnetic tape cartridgesrelates to a specific absolute longitudinal address, and appears every7.2 mm down the tape. Using prior art methods, an LPOS word comprises 36individual servo patterns, i.e. frames, wherein each frame encodes onebit of information. The LPOS values of two consecutive LPOS words differby one. Therefore, a tape drive can position a data/servo head assemblyat a specified LPOS address thereby achieving a longitudinal resolutionof about 7.2 mm.

A read/write assembly comprising two servo heads spans a data band andtwo servo bands disposed adjacent that data band. In the event one servohead is rendered inoperative, then only one servo head can be used tolaterally position the read/write head. Bit errors in the operativeservo channel can cause a stop-write condition.

Alternatively, a servo band may become damaged, or may not compriseuseful information resulting from media damage.

SUMMARY OF THE INVENTION

Applicant's invention comprises a sequential data storage medium, suchas for example and without limitation a magnetic tape, comprising asequence of plurality of servo patterns encoded therein, which providelateral position information and LPOS information. Each servo patterncomprises a first burst comprising a first pulse, a second pulse, athird pulse, a fourth pulse and a fifth pulse and a second burstcomprising a sixth pulse, a seventh pulse, an eighth pulse, a ninthpulse and a tenth pulse. The widths of the plurality of pulsescomprising the first burst and the second burst, in combination with thespacings between those pulses, encode two bits of data.

In certain embodiments, each servo pattern further comprises a thirdburst comprising an eleventh pulse, a twelfth pulse, a thirteenth pulse,and a fourteenth pulse, and a fourth burst comprising a fifteenth pulse,a sixteenth pulse, a seventeenth pulse, and an eighteenth pulse. Thewidths of the plurality of pulses comprising the third burst and thefourth burst, in combination with the spacings between the plurality ofpulses comprising the third burst and the fourth burst, encode one bitof data.

Applicant's invention further comprises a method to encode informationin a non-data region of Applicant's sequential data storage medium usingApplicant's servo pattern architecture. In certain embodiments,Applicant's method provides higher reliability of detection ofinformation and lower decoding latency as compared to prior artapproaches.

In certain embodiments, Applicant's method utilizes servo patternscomprising prior art Subframe 1 architecture in combination withApplicant's Subframe 2 architecture to encode 1 bit of information ineach servo pattern. In certain embodiments, Applicant's method utilizesservo patterns comprising Applicant's Subframe 1 architecture incombination with prior art Subframe 2 architecture to encode 2 bits ofinformation in each servo pattern. In certain embodiments, Applicant'smethod utilizes servo patterns comprising Applicant's Subframe 1architecture in combination with Applicant's Subframe 2 architecture toencode 3 bits of information in each servo pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from a reading of the followingdetailed description taken in conjunction with the drawings in whichlike reference designators are used to designate like elements, and inwhich:

FIG. 1A illustrates a servo pattern comprising four bursts, wherein eachof those four bursts comprises a plurality of pulses;

FIG. 1B illustrates widths and spacings for the pulses in Subframe 1 forthe servo pattern of FIG. 1A;

FIG. 1C illustrates widths and spacings for the pulses in Subframe 2 forthe servo pattern of FIG. 1A;

FIG. 2A illustrates a first prior art servo pattern used to encode asingle bit of information;

FIG. 2B illustrates widths and spacings for the pulses in Subframe 1 forthe servo pattern of FIG. 2A;

FIG. 3A illustrates a second prior art servo pattern used to encode asingle bit of information;

FIG. 3B illustrates widths and spacings for the pulses in Subframe 1 forthe servo pattern of FIG. 3A;

FIG. 4A illustrates a first embodiment of Applicant's Subframe 1architecture used to encode two bits of information having a value of“10”;

FIG. 4B illustrates a second embodiment of Applicant's Subframe 1architecture used to encode two bits of information having a value of“10”;

FIG. 5A illustrates a first embodiment of Applicant's Subframe 1architecture used to encode two bits of information having a value of“11”;

FIG. 5B illustrates a second embodiment of Applicant's Subframe 1architecture used to encode two bits of information having a value of“11”;

FIG. 6 illustrates Applicant's Subframe 1 architecture used to encodetwo bits of information having a value of “00”;

FIG. 7A illustrates a first embodiment of Applicant's Subframe 1architecture used to encode two bits of information having a value of“01”;

FIG. 7B illustrates a first embodiment of Applicant's Subframe 1architecture used to encode two bits of information having a value of“01”;

FIG. 8 illustrates Applicant's Subframe 2 architecture used to encodeone bit of information having a value of “1”; and

FIG. 9 illustrates Applicant's Subframe 2 architecture used to encodeone bit of information having a value of “0”.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is described in preferred embodiments in the followingdescription with reference to the Figures, in which like numbersrepresent the same or similar elements. Reference throughout thisspecification to “one embodiment,” “an embodiment,” or similar languagemeans that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the present invention. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” and similar language throughout thisspecification may, but do not necessarily, all refer to the sameembodiment.

The described features, structures, or characteristics of the inventionmay be combined in any suitable manner in one or more embodiments. Inthe following description, numerous specific details are recited toprovide a thorough understanding of embodiments of the invention. Oneskilled in the relevant art will recognize, however, that the inventionmay be practiced without one or more of the specific details, or withother methods, components, materials, and so forth. In other instances,well-known structures, materials, or operations are not shown ordescribed in detail to avoid obscuring aspects of the invention.

In sequential data storage media, such as for example magnetic tapestorage media, servo patterns are encoded in non-data portions of themedium. Those servo patterns are used to position a read/write head withrespect to a plurality of data tracks, to provide sync data, to providemanufacturer data, and to determine linear position (“LPOS”) along thelength of the medium.

Referring to FIG. 1A, recorded servo pattern 100 consists of transitionswith two different azimuthal slopes. Read/write head position is derivedfrom the relative timing of pulses generated by a narrow head readingthe pattern. Servo pattern 100 also allows the encoding of LPOSinformation without affecting the generation of the transversal positionerror signal (“PES”). Servo pattern 100 comprises Subframe 1 whichcomprises burst pattern 102 in combination with burst pattern 104, andSubframe 2 which comprises burst pattern 106 in combination with burstpattern 108.

FIG. 1B further illustrates the format of servo bursts 102 and 104,wherein bursts 102 and 104 do not encode information. Referring now toFIGS. 1A and 1B, servo burst 102 comprises servo stripes 1 thru 5 andcorresponding pulses 1 thru 5. Servo burst 104 comprises servo stripes 6thru 10 and corresponding pulses 6 thru 10.

Pulse 1 of burst 102 comprises a first magnetic phase shift 110, asecond magnetic phase shift 112, and a width w1 between phase shifts 110and 112. Pulse 2 of burst 102 comprises a third magnetic phase shift114, a fourth magnetic phase shift 116, and a width w2 between phaseshifts 114 and 116. A separation t1 separates first magnetic phase shift110 and third magnetic phase shift 114. A separation s1 separates secondmagnetic phase shift 112 and third magnetic phase shift 114.

Pulse 3 of burst 102 comprises a fifth magnetic phase shift 118, a sixthmagnetic phase shift 120, and a width w3 between phase shifts 118 and120. A separation t2 separates third magnetic phase shift 114 and fifthmagnetic phase shift 118. A separation s2 separates fourth magneticphase shift 116 and fifth magnetic phase shift 118.

Pulse 4 of burst 102 comprises a seventh magnetic phase shift 122, aneighth magnetic phase shift 124, and a width w4 between phase shifts 122and 124. A separation t3 separates fifth magnetic phase shift 118 andseventh magnetic phase shift 122. A separation s3 separates sixthmagnetic phase shift 120 and seventh magnetic phase shift 122.

Pulse 5 of burst 102 comprises a ninth magnetic phase shift 126, a tenthmagnetic phase shift 128, and a width w5 between phase shifts 126 and128. A separation t4 separates seventh magnetic phase shift 122 andninth magnetic phase shift 126. A separation s4 separates eighthmagnetic phase shift 124 and ninth magnetic phase shift 126.

Pulse 6 of burst 104 comprises an eleventh magnetic phase shift 130, atwelfth magnetic phase shift 132, and a width w6 between phase shifts130 and 132. Pulse 7 of burst 104 comprises a thirteenth magnetic phaseshift 134, a fourteenth magnetic phase shift 136, and a width w7 betweenphase shifts 134 and 136. A separation t6 separates eleventh magneticphase shift 130 and thirteenth magnetic phase shift 134. A separation s6separates twelfth magnetic phase shift 132 and thirteenth magnetic phaseshift 134.

Pulse 8 of burst 104 comprises a fifteenth magnetic phase shift 138, asixteenth magnetic phase shift 140, and a width w8 between phase shifts138 and 140. A separation t7 separates thirteenth magnetic phase shift134 and fifteenth magnetic phase shift 138. A separation s7 separatesfourteenth magnetic phase shift 136 and fifteenth magnetic phase shift138. Pulse 9 of burst 104 comprises a seventeenth magnetic phase shift142, an eighteenth magnetic phase shift 144, and a width w9 betweenphase shifts 142 and 144. A separation t8 separates fifteenth magneticphase shift 138 and seventeenth magnetic phase shift 142. A separations8 separates sixteenth magnetic phase shift 140 and seventeenth magneticphase shift 142.

Pulse 10 of burst 104 comprises a nineteenth magnetic phase shift 146, atwentieth magnetic phase shift 148, and a width w10 between phase shifts146 and 148. A separation t9 separates seventeenth magnetic phase shift142 and nineteenth magnetic phase shift 146. A separation s9 separateseighteenth magnetic phase shift 144 and nineteenth magnetic phase shift146.

In the non-encoded embodiment of bursts 102 and 104 illustrated in FIGS.1A and 1B, w1=w2=w3=w4=w5=w6=w7=w8=w9 w=10, t1=t2=t3=t4=t6=t7=t8=t9, ands1=s2=s3=s4=s6=s7=s8=s9. In certain embodiments, w1 through w10,inclusive, equal 2.0 microns, t1-t4 and t6-t9 equal 5.0 microns, ands1-s4 and s6-s9 equal 3.0 microns.

FIG. 1C further illustrates the format of servo bursts 106 and 108,wherein bursts 106 and 108 do not encode information. Referring now toFIGS. 1A and 1C, servo burst 106 comprises servo stripes 11 thru 14 andcorresponding pulses 11 thru 14. Servo burst 108 comprises servo stripes15 thru 18 and corresponding pulses 15 thru 18.

Pulse 11 of burst 106 comprises a first magnetic phase shift 150, asecond magnetic phase shift 152, and a width w11 between phase shifts150 and 152. Pulse 12 of burst 106 comprises a third magnetic phaseshift 154, a fourth magnetic phase shift 156, and a width w12 betweenphase shifts 154 and 156. A separation t11 separates first magneticphase shift 150 and third magnetic phase shift 154. A separation s11separates second magnetic phase shift 152 and third magnetic phase shift154.

Pulse 13 of burst 106 comprises a fifth magnetic phase shift 158, asixth magnetic phase shift 160, and a width w13 between phase shifts 158and 160. A separation t12 separates third magnetic phase shift 154 andfifth magnetic phase shift 158. A separation s12 separates fourthmagnetic phase shift 156 and fifth magnetic phase shift 158.

Pulse 14 of burst 106 comprises a seventh magnetic phase shift 162, aneighth magnetic phase shift 164, and a width w 14 between phase shifts162 and 164. A separation t13 separates fifth magnetic phase shift 158and seventh magnetic phase shift 162. A separation s13 separates sixthmagnetic phase shift 160 and seventh magnetic phase shift 162.

Pulse 15 of burst 108 comprises a ninth magnetic phase shift 166, atenth magnetic phase shift 168, and a width w15 between phase shifts 166and 168. Pulse 16 of burst 108 comprises an eleventh magnetic phaseshift 170, a twelfth magnetic phase shift 172, and a width w16 betweenphase shifts 170 and 172. A separation t15 separates ninth magneticphase shift 166 and eleventh magnetic phase shift 170. A separation s15separates tenth magnetic phase shift 168 and eleventh magnetic phaseshift 170.

Pulse 17 of burst 108 comprises a thirteenth magnetic phase shift 174, afourteenth magnetic phase shift 176, and a width w17 between phaseshifts 174 and 176. A separation t16 separates eleventh magnetic phaseshift 170 and thirteenth magnetic phase shift 174. A separation s16separates twelfth magnetic phase shift 172 and thirteenth magnetic phaseshift 174.

Pulse 18 of burst 108 comprises a fifteenth magnetic phase shift 178, asixteenth magnetic phase shift 180, and a width w18 between phase shifts178 and 180. A separation t17 separates thirteenth magnetic phase shift174 and fifteenth magnetic phase shift 178. A separation s17 separatesfourteenth magnetic phase shift 176 and fifteenth magnetic phase shift178.

In the non-encoded embodiment of bursts 106 and 108 illustrated in FIGS.1A and 1C, w11=w12=w13=w14=w15=w16=w17=w18, t11=t12=t13=t15=t16=t17, ands11=s12=s13 s15=s16=s17. In certain embodiments, w11 through 18,inclusive, equal 2.0 microns, t11-t13 and t15-t17 equal 5.0 microns, ands11-s13 and s15-s17 equal 3.0 microns.

FIG. 2A shows prior art servo pattern 200. The spacings between thepulses in Subframe 1, i.e. bursts 202 and 204, have been altered withrespect to the nominal spacings shown in FIGS. 1A and 1B. The widths w1through w10 of the pulses in bursts 202 and 204 are equal. Using priorart methods, servo pattern 200 encodes a bit of information, whereinthat bit is decoded to comprise a value of “1”.

Referring now to FIGS. 2A and 2B, pulse 2 in burst 202, and pulse 7 inburst 204, are shifted a distance of −250 nanometers from the nominalplacements of pulses 2 and 7 in bursts 102 and 104, respectively. Inaddition, pulse 4 in burst 202, and pulse 9 in burst 204, are shifted adistance of +250 nanometers from the nominal placements pulses 4 and 9in bursts 102 and 104, respectively. As a result, t1′ and t4′ in burst202 are decreased to 4.75 nanometers, and t2′ and t3′ in burst 202 areincreased to 5.25 nanometers. Similarly, t6′ and t9′ in burst 204 aredecreased to 4.75 nanometers, and t7′ and t8′ in burst 204 are increasedto 5.25 nanometers.

FIG. 3A shows prior art servo pattern 300. The spacings between thepulses in Subframe 1, i.e. bursts 302 and 304, have been altered withrespect to the nominal spacings shown in FIGS. 1A and 1B. The widths w1through w10 of the pulses in bursts 302 and 304 are equal. Using priorart methods, servo pattern 300 encodes a bit of information, whereinthat bit is decoded to comprise a value of “0”.

Referring now to FIGS. 3A and 3B, pulse 2 in burst 302, and pulse 7 inburst 304, are shifted a distance of +250 nanometers from the nominalplacements of pulses 2 and 7 in bursts 102 and 104, respectively. Inaddition, pulse 4 in burst 302, and pulse 9 in burst 304, are shifted adistance of −250 nanometers from the nominal placements of pulses 4 and9 in bursts 102 and 104, respectively. As a result, t1′ and t4′ in burst302 are increased to 5.25 nanometers, and t2′ and t3′ in burst 302 aredecreased to 4.75 nanometers. Similarly, t6′ and t9′ in burst 304 areincreased to 5.25 nanometers, and t7′ and t8′ in burst 304 are decreasedto 4.75 nanometers.

In certain embodiments, Applicant's servo pattern architecture utilizesa Subframe 1 that encodes 2 bits of information in combination withprior art Subframe 2 that does not encode any information. FIGS. 4, 5,6, and 7, illustrate Applicant's Subframe 1 architectures.

In certain embodiments, Applicant's servo pattern architecture utilizesa Subframe 1 that encodes 2 bits of information in combination withApplicant's Subframe 2 architecture that encodes one bit of information.FIGS. 8 and 9 illustrate Applicant's Subframe 2 architectures.

FIG. 4A illustrates non-encoded bursts 102 and 104, and Applicant'sservo bursts 402A and 404A. Applicant's servo bursts 402 and 404 encodeinformation having a value of “10”.

Referring now to FIG. 4A, pulse 1 of burst 402A comprises a firstmagnetic phase shift 410A, a second magnetic phase shift 412A, and awidth w1′ between phase shifts 410A and 412A. Pulse 2 of burst 402Acomprises a third magnetic phase shift 414A, a fourth magnetic phaseshift 416A, and a width w2′ between phase shifts 414A and 416A. Aseparation t1′ separates first magnetic phase shift 410A and thirdmagnetic phase shift 414A. A separation s1′ separates second magneticphase shift 412A and third magnetic phase shift 414A.

Pulse 3 of burst 402A comprises a fifth magnetic phase shift 418A, asixth magnetic phase shift 420A, and a width w3′ between phase shifts418A and 420A. A separation t2′ separates third magnetic phase shift414A and fifth magnetic phase shift 418A. A separation s2′ separatesfourth magnetic phase shift 416A and fifth magnetic phase shift 418A.

Pulse 4 of burst 402A comprises a seventh magnetic phase shift 422A aneighth magnetic phase shift 424A, and a width w4′ between phase shifts422A and 424A. A separation t3′ separates fifth magnetic phase shift418A and seventh magnetic phase shift 422A. A separation s3′ separatessixth magnetic phase shift 420A and seventh magnetic phase shift 422A.Pulse 5 of burst 402A comprises a ninth magnetic phase shift 426A, atenth magnetic phase shift 428A, and a width w5′ between phase shifts426A and 428A. A separation t4′ separates seventh magnetic phase shift422A and ninth magnetic phase shift 426A. A separation s4′ separateseighth magnetic phase shift 424A and ninth magnetic phase shift 426A.

Pulse 6 of burst 404A comprises an eleventh magnetic phase shift 430A, atwelfth magnetic phase shift 432A, and a width w6′ between phase shifts430A and 432A. Pulse 7 of burst 404A comprises a thirteenth magneticphase shift 434A, a fourteenth magnetic phase shift 436A, and a widthw7′ between phase shifts 434A and 436A. A separation t6′ separateseleventh magnetic phase shift 430A and thirteenth magnetic phase shift434A. A separation s6′ separates twelfth magnetic phase shift 432A andthirteenth magnetic phase shift 434A.

Pulse 8 of burst 404A comprises a fifteenth magnetic phase shift 438A, asixteenth magnetic phase shift 440A, and a width w8′ between phaseshifts 438A and 440A. A separation t7′ separates thirteenth magneticphase shift 434A and fifteenth magnetic phase shift 438A. A separations7′ separates fourteenth magnetic phase shift 436A and fifteenthmagnetic phase shift 438A. Pulse 9 of burst 404A comprises a seventeenthmagnetic phase shift 442A, an eighteenth magnetic phase shift 444A, anda width w9′ between phase shifts 442A and 444A. A separation t8′separates fifteenth magnetic phase shift 438A and seventeenth magneticphase shift 442A. A separation s8′ separates sixteenth magnetic phaseshift 440A and seventeenth magnetic phase shift 442A.

Pulse 10 of burst 404A comprises a nineteenth magnetic phase shift 446A,a twentieth magnetic phase shift 448A, and a width w10′ between phaseshifts 446A and 448A. A separation t9′ separates seventeenth magneticphase shift 442A and nineteenth magnetic phase shift 446A. A separations9′ separates eighteenth magnetic phase shift 444A and nineteenthmagnetic phase shift 446A.

In the illustrated embodiment of FIG. 4A, in bursts 402A and 404Aw1′=w3′=w5′=w6′=w8′=w10′. In certain embodiments, in burst 402A and 404Aw1′=w3′=w5′=w6′=w8′=w10′=2.0 microns. In the illustrated embodiment ofFIG. 4A, in bursts 402A and 404A w2′=w4′=w7′=w9′. In certainembodiments, in bursts 402A and 404A w2′=w4′=w7′=w9′=2.25 microns.

In certain embodiments, in burst 402A and 404A, t1′=t6′. In certainembodiments, in burst 402A and 404A, t1′=t6′4.75 microns. In certainembodiments, in bursts 402A and 404A t2′=t7′. In certain embodiments, inbursts 402A and 404A, t2′=t7′=5.25 microns. In certain embodiments, inburst 402A and 404A, t3′=t4′=t8′=t9′. In certain embodiments, in burst402A and 404A, t3′=t4′=t8′=t9′=5.0 microns.

In certain embodiments, in bursts 402A and 404A, s1′=s4′=s6′=s9′. Incertain embodiments, in bursts 402A and 404A, s1′=s4′=s6′=s9′=2.75microns. In certain embodiments, in bursts 402A and 404A,s2′=s3′=s7′=s8′. In certain embodiments, in bursts 402A and 404A,s2′=s3′=s7′=s8′=3.0 microns.

FIG. 4B illustrates non-encoded bursts 102 and 104, and Applicant'sservo bursts 402B and 404B. Applicant's servo bursts 402B and 404Bencode information having a value of “10”.

Referring now to FIG. 4B, pulse 1 of burst 402B comprises a firstmagnetic phase shift 410B, a second magnetic phase shift 412B, and awidth w1′ between phase shifts 410B and 412B. Pulse 2 of burst 402Bcomprises a third magnetic phase shift 414B, a fourth magnetic phaseshift 416B, and a width w2′ between phase shifts 414B and 416B. Aseparation t1′ separates first magnetic phase shift 410B and thirdmagnetic phase shift 414B. A separation s1′ separates second magneticphase shift 412B and third magnetic phase shift 414B.

Pulse 3 of burst 402B comprises a fifth magnetic phase shift 418B, asixth magnetic phase shift 420B, and a width w3′ between phase shifts418B and 420B. A separation t2′ separates third magnetic phase shift414B and fifth magnetic phase shift 418B. A separation s2′ separatesfourth magnetic phase shift 416B and fifth magnetic phase shift 418B.

Pulse 4 of burst 402B comprises a seventh magnetic phase shift 422B, aneighth magnetic phase shift 424B, and a width w4′ between phase shifts422B and 424B. A separation t3′ separates fifth magnetic phase shift418B and seventh magnetic phase shift 422B. A separation s3′ separatessixth magnetic phase shift 420B and seventh magnetic phase shift 422B.Pulse 5 of burst 402B comprises a ninth magnetic phase shift 426B, atenth magnetic phase shift 428B, and a width w5′ between phase shifts426B and 428B. A separation t4′ separates seventh magnetic phase shift422B and ninth magnetic phase shift 426B. A separation s4′ separateseighth magnetic phase shift 424B and ninth magnetic phase shift 426B.

Pulse 6 of burst 404B comprises an eleventh magnetic phase shift 430B, atwelfth magnetic phase shift 432B, and a width w6′ between phase shifts430B and 432B. Pulse 7 of burst 404B comprises a thirteenth magneticphase shift 434B, a fourteenth magnetic phase shift 436B, and a widthw7′ between phase shifts 434B and 436B. A separation t6′ separateseleventh magnetic phase shift 430B and thirteenth magnetic phase shift434B. A separation s6′ separates twelfth magnetic phase shift 432B andthirteenth magnetic phase shift 434B.

Pulse 8 of burst 404B comprises a fifteenth magnetic phase shift 438B, asixteenth magnetic phase shift 440B, and a width w8′ between phaseshifts 438B and 440B. A separation t7′ separates thirteenth magneticphase shift 434B and fifteenth magnetic phase shift 438B. A separations7′ separates fourteenth magnetic phase shift 436B and fifteenthmagnetic phase shift 438B. Pulse 9 of burst 404B comprises a seventeenthmagnetic phase shift 442B, an eighteenth magnetic phase shift 444B, anda width w9′ between phase shifts 442B and 444B. A separation t8′separates fifteenth magnetic phase shift 438B and seventeenth magneticphase shift 442B. A separation s8′ separates sixteenth magnetic phaseshift 440B and seventeenth magnetic phase shift 442B.

Pulse 10 of burst 404B comprises a nineteenth magnetic phase shift 446B,a twentieth magnetic phase shift 448B, and a width w10′ between phaseshifts 446B and 448B. A separation t9′ separates seventeenth magneticphase shift 442B and nineteenth magnetic phase shift 446B. A separations9′ separates eighteenth magnetic phase shift 444B and nineteenthmagnetic phase shift 446B.

In the illustrated embodiment of FIG. 4B, in bursts 402B and 404Bw1′=w3′=w5′=w6′=w8′=w10′. In certain embodiments, in burst 402B and404B, w1′=w3′=w5′=w6′=w8′=w10′=2.0 microns. In the illustratedembodiment of FIG. 4B, in bursts 402B and 404B, w2′=w4′=w7′=w9′. Incertain embodiments, in bursts 402B and 404B, w2′=w4′=w7′=w9′=2.5microns.

In certain embodiments, in burst 402B and 404B, t1′=t3′=t6′=t8′. Incertain embodiments, in burst 402B and 404B, t1′=t3′=t6′=t8′=4.75microns. In certain embodiments, in bursts 402B and 404B,t2′=t4′=t7′=t9′. In certain embodiments, in bursts 402B and 404B,t2′=t4′=t7′=t9′=5.25 microns.

In certain embodiments, in bursts 402B and 404B,s1′=s2′=s3′=s4′=s6′=s7′=s8′=s9′. In certain embodiments, in bursts 402Band 404B, s1′=s2′=s3′=s4′=s6′=s7′=s8′=s9′=2.75 microns.

FIG. 5A illustrates non-encoded bursts 102 and 104, and Applicant'sservo bursts 502A and 504A. In certain embodiments of Applicant'sSubframe 1 architecture, Applicant's servo bursts 502A and 504A encodeinformation having a value of “11”. Referring now to FIG. 5A, pulse 1 ofburst 502A comprises a first magnetic phase shift 510A, a secondmagnetic phase shift 512A, and a width w1′ between phase shifts 510A and512A. Pulse 2 of burst 502A comprises a third magnetic phase shift 514A,a fourth magnetic phase shift 516A, and a width w2′ between phase shifts514A and 516A. A separation t1′ separates first magnetic phase shift510A and third magnetic phase shift 514A. A separation s1′ separatessecond magnetic phase shift 512A and third magnetic phase shift 514A.

Pulse 3 of burst 502A comprises a fifth magnetic phase shift 518A, asixth magnetic phase shift 520A, and a width w3′ between phase shifts518A and 520A. A separation t2′ separates third magnetic phase shift514A and fifth magnetic phase shift 518A. A separation s2′ separatesfourth magnetic phase shift 516A and fifth magnetic phase shift 518A.

Pulse 4 of burst 502A comprises a seventh magnetic phase shift 522A, aneighth magnetic phase shift 524A, and a width w4′ between phase shifts522A and 524A. A separation t3′ separates fifth magnetic phase shift518A and seventh magnetic phase shift 522A. A separation s3′ separatessixth magnetic phase shift 520A and seventh magnetic phase shift 522A.Pulse 5 of burst 502A comprises a ninth magnetic phase shift 526A, atenth magnetic phase shift 528A, and a width w5′ between phase shifts526A and 528A. A separation t4′ separates seventh magnetic phase shift522A and ninth magnetic phase shift 526A. A separation s4′ separateseighth magnetic phase shift 524A and ninth magnetic phase shift 526A.

Pulse 6 of burst 504A comprises an eleventh magnetic phase shift 530A, atwelfth magnetic phase shift 532A, and a width w6′ between phase shifts530A and 532A. Pulse 7 of burst 504A comprises a thirteenth magneticphase shift 534A, a fourteenth magnetic phase shift 536A, and a widthw7′ between phase shifts 534A and 536A. A separation t6′ separateseleventh magnetic phase shift 530A and thirteenth magnetic phase shift534A. A separation s6′ separates twelfth magnetic phase shift 532A andthirteenth magnetic phase shift 534A.

Pulse 8 of burst 504A comprises a fifteenth magnetic phase shift 538A, asixteenth magnetic phase shift 540A, and a width w8′ between phaseshifts 538A and 540A. A separation t7′ separates thirteenth magneticphase shift 534A and fifteenth magnetic phase shift 538A. A separations7′ separates fourteenth magnetic phase shift 536A and fifteenthmagnetic phase shift 538A. Pulse 9 of burst 504A comprises a seventeenthmagnetic phase shift 542A, an eighteenth magnetic phase shift 544A, anda width w9′ between phase shifts 542A and 544A. A separation t8′separates fifteenth magnetic phase shift 538A and seventeenth magneticphase shift 542A. A separation s8′ separates sixteenth magnetic phaseshift 540A and seventeenth magnetic phase shift 542A.

Pulse 10 of burst 504A comprises a nineteenth magnetic phase shift 546A,a twentieth magnetic phase shift 548A, and a width w10′ between phaseshifts 546A and 548A. A separation t9′ separates seventeenth magneticphase shift 542A and nineteenth magnetic phase shift 546A. A separations9′ separates eighteenth magnetic phase shift 544A and nineteenthmagnetic phase shift 546A.

In the illustrated embodiment of FIG. 5A, in bursts 502A and 504A,w1′=w2′=w3′=w4′=w5′=w6′=w7′=w8′=w9′=w10′. In certain embodiments, inburst 502A and 504A, w1′=w2′=w3′=w4′=w5′=w6′=w7′=w8′=w9′=w10′=2.0microns.

In certain embodiments, in burst 502A and 504A, t1′=t4′=t6′=t9′. Incertain embodiments, in burst 502A and 504A, t1′=t4′=t6′=t9′=4.75microns. In certain embodiments, in bursts 502A and 504At2′=t3′=t7′=t8′. In certain embodiments, in bursts 502A and 504A,t2′=t3′=t7′=t8′=5.25 microns.

In certain embodiments, in bursts 502A and 504A, s1′=s4′=s6′=s9′. Incertain embodiments, in bursts 502A and 504A, s1′=s4′=s6′=s9′=2.75microns. In certain embodiments, in bursts 502A and 504A,s2′=s3′=s7′=s8′. In certain embodiments, in bursts 502A and 504A,s2′=s3′=s7′=s8′=3.25 microns.

FIG. 5B illustrates non-encoded bursts 102 and 104, and Applicant'sservo bursts 502B and 504B. In certain embodiments of Applicant'sSubframe 1 architecture, Applicant's servo bursts 502B and 504B encodeinformation having a value of “11”. Burst 502B comprises the samepulses, pulse widths, and pulse separations as does burst 102. Burst504B comprises the same pulses, pulse widths, and pulse separations asdoes burst 104.

Referring now to FIG. 5B, pulse 1 of burst 502B comprises a firstmagnetic phase shift 510B, a second magnetic phase shift 512B, and awidth w1′ between phase shifts 510B and 512B. Pulse 2 of burst 502Bcomprises a third magnetic phase shift 514B, a fourth magnetic phaseshift 516B, and a width w2′ between phase shifts 514B and 516B. Aseparation t1′ separates first magnetic phase shift 510B and thirdmagnetic phase shift 514B. A separation s1′ separates second magneticphase shift 512B and third magnetic phase shift 514B.

Pulse 3 of burst 502B comprises a fifth magnetic phase shift 518B, asixth magnetic phase shift 520B, and a width w3′ between phase shifts518B and 520B. A separation t2′ separates third magnetic phase shift514B and fifth magnetic phase shift 518B. A separation s2′ separatesfourth magnetic phase shift 516B and fifth magnetic phase shift 518B.

Pulse 4 of burst 502B comprises a seventh magnetic phase shift 522B, aneighth magnetic phase shift 524B, and a width w4′ between phase shifts522B and 524B. A separation t3′ separates fifth magnetic phase shift518B and seventh magnetic phase shift 522B. A separation s3′ separatessixth magnetic phase shift 520B and seventh magnetic phase shift 522B.Pulse 5 of burst 502B comprises a ninth magnetic phase shift 526B, atenth magnetic phase shift 528B, and a width w5′ between phase shifts526B and 528B. A separation t4′ separates seventh magnetic phase shift522B and ninth magnetic phase shift 526B. A separation s4′ separateseighth magnetic phase shift 524B and ninth magnetic phase shift 526B.

Pulse 6 of burst 504B comprises an eleventh magnetic phase shift 530B, atwelfth magnetic phase shift 532B, and a width w6′ between phase shifts530B and 532B. Pulse 7 of burst 504B comprises a thirteenth magneticphase shift 534B, a fourteenth magnetic phase shift 536B, and a widthw7′ between phase shifts 534B and 536B. A separation t6′ separateseleventh magnetic phase shift 530B and thirteenth magnetic phase shift534B. A separation s6′ separates twelfth magnetic phase shift 532B andthirteenth magnetic phase shift 534B.

Pulse 8 of burst 504B comprises a fifteenth magnetic phase shift 538B, asixteenth magnetic phase shift 540B, and a width w8′ between phaseshifts 538B and 540B. A separation t7′ separates thirteenth magneticphase shift 534B and fifteenth magnetic phase shift 538B. A separations7′ separates fourteenth magnetic phase shift 536B and fifteenthmagnetic phase shift 538B. Pulse 9 of burst 504B comprises a seventeenthmagnetic phase shift 542B, an eighteenth magnetic phase shift 544B, anda width w9′ between phase shifts 542B and 544B. A separation t8′separates fifteenth magnetic phase shift 538B and seventeenth magneticphase shift 542B. A separation s8′ separates sixteenth magnetic phaseshift 540B and seventeenth magnetic phase shift 542B.

Pulse 10 of burst 504B comprises a nineteenth magnetic phase shift 546B,a twentieth magnetic phase shift 548B, and a width w10′ between phaseshifts 546B and 548B. A separation t9′ separates seventeenth magneticphase shift 542B and nineteenth magnetic phase shift 546B. A separations9′ separates eighteenth magnetic phase shift 544B and nineteenthmagnetic phase shift 546B.

In the illustrated embodiment of FIG. 5B, in bursts 502B and 504B,w1′=w2′=w3′=w4′=w5′=w6′=w7′=w8′=w9′=w10′. In certain embodiments, inburst 502B and 504B, w1′=w2′=w3′=w4′=w5′=w6′=w7′=w8′=w9′=w10′=2.0microns. In certain embodiments, in burst 502B and 504B,t1′=t2′=t3′=t4′=t5′=t6′=t7′=t8′=t9′. In certain embodiments, in burst502B and 504B, t1′=t2′=t3′=t4′=t5′=t6′=t7′=t8′=t9′=5.0 microns. Incertain embodiments, in bursts 502A and 504A,s1′=s2′=s3′=s4′=s5′=s6′=s7′=s8′=s9′. In certain embodiments, in bursts502A and 504A, s1′=s2′=s3′=s4′=s5′=s6′=s7′=s8′=s9′=3.0 microns.

FIG. 6 illustrates non-encoded bursts 102 and 104, and Applicant's servobursts 602 and 604. Applicant's servo bursts 602 and 604 encodeinformation having a value of “00”. Referring now to FIG. 6, pulse 1 ofburst 602 comprises a first magnetic phase shift 610, a second magneticphase shift 612, and a width w1′ between phase shifts 610 and 612. Pulse2 of burst 602 comprises a third magnetic phase shift 614, a fourthmagnetic phase shift 616, and a width w2′ between phase shifts 614 and616. A separation t1′ separates first magnetic phase shift 610 and thirdmagnetic phase shift 614. A separation s1′ separates second magneticphase shift 612 and third magnetic phase shift 614.

Pulse 3 of burst 602 comprises a fifth magnetic phase shift 618, a sixthmagnetic phase shift 620, and a width w3′ between phase shifts 618 and620. A separation t2′ separates third magnetic phase shift 614 and fifthmagnetic phase shift 618. A separation s2′ separates fourth magneticphase shift 616 and fifth magnetic phase shift 618.

Pulse 4 of burst 602 comprises a seventh magnetic phase shift 622, aneighth magnetic phase shift 624, and a width w4′ between phase shifts622 and 624. A separation t3′ separates fifth magnetic phase shift 618and seventh magnetic phase shift 622. A separation s3′ separates sixthmagnetic phase shift 620 and seventh magnetic phase shift 622. Pulse 5of burst 602 comprises a ninth magnetic phase shift 626, a tenthmagnetic phase shift 628, and a width w5′ between phase shifts 626 and628. A separation t4′ separates seventh magnetic phase shift 622 andninth magnetic phase shift 626. A separation s4′ separates eighthmagnetic phase shift 624 and ninth magnetic phase shift 626.

Pulse 6 of burst 604 comprises an eleventh magnetic phase shift 630, atwelfth magnetic phase shift 632, and a width w6′ between phase shifts630 and 632. Pulse 7 of burst 604 comprises a thirteenth magnetic phaseshift 634, a fourteenth magnetic phase shift 636, and a width w7′between phase shifts 634 and 636. A separation t6′ separates eleventhmagnetic phase shift 630 and thirteenth magnetic phase shift 634. Aseparation s6′ separates twelfth magnetic phase shift 632 and thirteenthmagnetic phase shift 634.

Pulse 8 of burst 604 comprises a fifteenth magnetic phase shift 638, asixteenth magnetic phase shift 640, and a width w8′ between phase shifts638 and 640. A separation t7′ separates thirteenth magnetic phase shift634 and fifteenth magnetic phase shift 638. A separation s7′ separatesfourteenth magnetic phase shift 636 and fifteenth magnetic phase shift638. Pulse 9 of burst 604 comprises a seventeenth magnetic phase shift642, an eighteenth magnetic phase shift 644, and a width w9′ betweenphase shifts 642 and 644. A separation t8′ separates fifteenth magneticphase shift 638 and seventeenth magnetic phase shift 642. A separations8′ separates sixteenth magnetic phase shift 640 and seventeenthmagnetic phase shift 642.

Pulse 10 of burst 604 comprises a nineteenth magnetic phase shift 646, atwentieth magnetic phase shift 648, and a width w10′ between phaseshifts 646 and 648. A separation t9′ separates seventeenth magneticphase shift 642 and nineteenth magnetic phase shift 646. A separations9′ separates eighteenth magnetic phase shift 644 and nineteenthmagnetic phase shift 646.

In the illustrated embodiment of FIG. 6, in bursts 602 and 604,w1′=w2′=w3′=w4′=w5′=w6′=w7′=w8′=w9′=w10′. In certain embodiments, inburst 602 and 604, w1′=w2′=w3′=w4′=w5′=w6′=w7′=w8′=w9′=w10′=2.0 microns.

In certain embodiments, in burst 602 and 604, t1′=t4′=t6′=t9′. Incertain embodiments, in burst 602 and 604, t1′=t4′=t6′=t9′=5.25 microns.In certain embodiments, in bursts 602 and 604, t2′=t3′=t7′=t8′. Incertain embodiments, in bursts 602 and 604, t2′=t3′=t7′=t8′=4.75microns.

In certain embodiments, in bursts 602 and 604, s1′=s4′=s6′=s9′. Incertain embodiments, in bursts 602 and 604, s1′=s4′=s6′=s9′=3.25microns. In certain embodiments, in bursts 602 and 604, s2′=s3′=s7′=s8′.In certain embodiments, in bursts 602 and 604, s2′=s3′=s7′=s8′=2.75microns.

FIG. 7A illustrates non-encoded bursts 102 and 104, and Applicant'sservo bursts 702A and 704A. Applicant's servo bursts 702A and 704Aencode information having a value of “01”. Referring now to FIG. 7A,pulse 1 of burst 702A comprises a first magnetic phase shift 710A, asecond magnetic phase shift 712A, and a width w1′ between phase shifts710A and 712A. Pulse 2 of burst 702A comprises a third magnetic phaseshift 714A, a fourth magnetic phase shift 716A, and a width w2′ betweenphase shifts 714A and 716A. A separation t1′ separates first magneticphase shift 710A and third magnetic phase shift 714A. A separation s1′separates second magnetic phase shift 712A and third magnetic phaseshift 714A.

Pulse 3 of burst 702A comprises a fifth magnetic phase shift 718A, asixth magnetic phase shift 720A, and a width w3′ between phase shifts718A and 720A. A separation t2′ separates third magnetic phase shift714A and fifth magnetic phase shift 718A. A separation s2′ separatesfourth magnetic phase shift 716A and fifth magnetic phase shift 718A.

Pulse 4 of burst 702A comprises a seventh magnetic phase shift 722A, aneighth magnetic phase shift 724A, and a width w4′ between phase shifts722A and 724A. A separation t3′ separates fifth magnetic phase shift718A and seventh magnetic phase shift 722A. A separation s3′ separatessixth magnetic phase shift 720A and seventh magnetic phase shift 722A.Pulse 5 of burst 702A comprises a ninth magnetic phase shift 726A, atenth magnetic phase shift 728A, and a width w5′ between phase shifts726A and 728A. A separation t4′ separates seventh magnetic phase shift722A and ninth magnetic phase shift 726A. A separation s4′ separateseighth magnetic phase shift 724A and ninth magnetic phase shift 726A.

Pulse 6 of burst 704A comprises an eleventh magnetic phase shift 730A, atwelfth magnetic phase shift 732A, and a width w6′ between phase shifts730A and 732A. Pulse 7 of burst 704A comprises a thirteenth magneticphase shift 734A, a fourteenth magnetic phase shift 736A, and a widthw7′ between phase shifts 734A and 736A. A separation t6′ separateseleventh magnetic phase shift 730A and thirteenth magnetic phase shift734A. A separation s6′ separates twelfth magnetic phase shift 732A andthirteenth magnetic phase shift 734A.

Pulse 8 of burst 704A comprises a fifteenth magnetic phase shift 738A, asixteenth magnetic phase shift 740A, and a width w8′ between phaseshifts 738A and 740A. A separation t7′ separates thirteenth magneticphase shift 734A and fifteenth magnetic phase shift 738A. A separations7′ separates fourteenth magnetic phase shift 736A and fifteenthmagnetic phase shift 738A. Pulse 9 of burst 704A comprises a seventeenthmagnetic phase shift 742A, an eighteenth magnetic phase shift 744A, anda width w9′ between phase shifts 742A and 744A. A separation t8′separates fifteenth magnetic phase shift 738A and seventeenth magneticphase shift 742A. A separation s8′ separates sixteenth magnetic phaseshift 740A and seventeenth magnetic phase shift 742A.

Pulse 10 of burst 704A comprises a nineteenth magnetic phase shift 746A,a twentieth magnetic phase shift 748A, and a width w10′ between phaseshifts 746A and 748A. A separation t9′ separates seventeenth magneticphase shift 742A and nineteenth magnetic phase shift 746A. A separations9′ separates eighteenth magnetic phase shift 744A and nineteenthmagnetic phase shift 746A.

In the illustrated embodiment of FIG. 7A, in bursts 702A and 704A,w1′=w3′=w5′=w6′=w8′=w10′. In certain embodiments, in burst 702 and 704,w1′=w3′=w5′=w6′=w8′=w10′=2.0 microns. In the illustrated embodiment ofFIG. 7A, in bursts 702 and 704, w2′=w4′=w7′=w9′. In certain embodiments,in bursts 702A and 704A, w2′=w4′=w7′=w9′=2.5 microns.

In certain embodiments, in burst 702A and 704A, t1′=t2′=t6′=t7′. Incertain embodiments, in burst 702A and 704A, t1′=t2′=t6′=t7′=5.0microns. In certain embodiments, in bursts 702A and 704A, t3′=t8′. Incertain embodiments, in bursts 702A and 704A, t3′=t8′=4.5 microns. Incertain embodiments, in bursts 702A and 704A t4′=t9′. In certainembodiments, in bursts 702A and 704A, t4′=t9′=5.5 microns.

In certain embodiments, in bursts 702A and 704A, s1′=s4′=s6′=s9′. Incertain embodiments, in bursts 702A and 704A, s1′=s4′=s6′=s9′=3.0microns. In certain embodiments, in bursts 702A and 704A,s2′=s3=s7′=s8′. In certain embodiments, in bursts 702A and 704A,s2′=s3′=s7′=s8′=2.5 microns.

FIG. 7B illustrates non-encoded bursts 102 and 104, and Applicant'sservo bursts 702B and 704B. Applicant's servo bursts 702B and 704Bencode information having a value of “01”. Referring now to FIG. 7B,pulse 1 of burst 702B comprises a first magnetic phase shift 710B, asecond magnetic phase shift 712B, and a width w1′ between phase shifts710B and 712B. Pulse 2 of burst 702B comprises a third magnetic phaseshift 714B, a fourth magnetic phase shift 716B, and a width w2′ betweenphase shifts 714B and 716B. A separation t1′ separates first magneticphase shift 710B and third magnetic phase shift 714B. A separation s1′separates second magnetic phase shift 712B and third magnetic phaseshift 714B. Pulse 3 of burst 702B comprises a fifth magnetic phase shift718B, a sixth magnetic phase shift 720B, and a width w3′ between phaseshifts 718B and 720B. A separation t2′ separates third magnetic phaseshift 714B and fifth magnetic phase shift 718B. A separation s2′separates fourth magnetic phase shift 716B and fifth magnetic phaseshift 718B.

Pulse 4 of burst 702B comprises a seventh magnetic phase shift 722B, aneighth magnetic phase shift 724B, and a width w4′ between phase shifts722B and 724B. A separation t3′ separates fifth magnetic phase shift718B and seventh magnetic phase shift 722B. A separation s3′ separatessixth magnetic phase shift 720B and seventh magnetic phase shift 722B.Pulse 5 of burst 702B comprises a ninth magnetic phase shift 726B, atenth magnetic phase shift 728B, and a width w5′ between phase shifts726B and 728B. A separation t4′ separates seventh magnetic phase shift722B and ninth magnetic phase shift 726B. A separation s4′ separateseighth magnetic phase shift 724B and ninth magnetic phase shift 726B.

Pulse 6 of burst 704B comprises an eleventh magnetic phase shift 730B, atwelfth magnetic phase shift 732B, and a width w6′ between phase shifts730B and 732B. Pulse 7 of burst 704B comprises a thirteenth magneticphase shift 734B, a fourteenth magnetic phase shift 736B, and a widthw7′ between phase shifts 734B and 736B. A separation t6′ separateseleventh magnetic phase shift 730B and thirteenth magnetic phase shift734B. A separation s6′ separates twelfth magnetic phase shift 732B andthirteenth magnetic phase shift 734B.

Pulse 8 of burst 704B comprises a fifteenth magnetic phase shift 738B, asixteenth magnetic phase shift 740B, and a width w8′ between phaseshifts 738B and 740B. A separation t7′ separates thirteenth magneticphase shift 734B and fifteenth magnetic phase shift 738B. A separations7′ separates fourteenth magnetic phase shift 736B and fifteenthmagnetic phase shift 738B. Pulse 9 of burst 704B comprises a seventeenthmagnetic phase shift 742B, an eighteenth magnetic phase shift 744B, anda width w9′ between phase shifts 742B and 744B. A separation t8′separates fifteenth magnetic phase shift 738B and seventeenth magneticphase shift 742B. A separation s8′ separates sixteenth magnetic phaseshift 740B and seventeenth magnetic phase shift 742B.

Pulse 10 of burst 704B comprises a nineteenth magnetic phase shift 746B,a twentieth magnetic phase shift 748B, and a width w10′ between phaseshifts 746B and 748B. A separation t9′ separates seventeenth magneticphase shift 742B and nineteenth magnetic phase shift 746B. A separations9′ separates eighteenth magnetic phase shift 744B and nineteenthmagnetic phase shift 746B.

In the illustrated embodiment of FIG. 7B, in bursts 702B and 704B,w1′=w3′=w5′=w6′=w8′=w10′. In certain embodiments, in burst 702B and704B, w1′=w3′=w5′=w6′=w8′=w10′=2.0 microns. In the illustratedembodiment of FIG. 7B, in bursts 702B and 704B, w2′=w4′=w7′=w9′. Incertain embodiments, in bursts 702B and 704B, w2′=w4′=w7′=w9′=2.25microns.

In certain embodiments, in burst 702B and 704B, t1′=t2′=t6′=t7′. Incertain embodiments, in burst 702B and 704B, t1′=t2′=t6′=t7′=5.0microns. In certain embodiments, in bursts 702B and 704B, t3′=t8′. Incertain embodiments, in bursts 702B and 704, t3′=t8′=4.75 microns. Incertain embodiments, in bursts 702B and 704B, t4′=t9′. In certainembodiments, in bursts 702B and 704B, t4′=t9′=5.25 microns.

In certain embodiments, in bursts 702B and 704B, s1′=s4′=s6′=s9′. Incertain embodiments, in bursts 702B and 70B, s1′=s4′=s6′=s9′=3.0microns. In certain embodiments, in bursts 702B and 704B,s2′=s3′=s7′=s8″. In certain embodiments, in bursts 702B and 704B,s2′=s3′=s7′=s8′=2.75 microns.

FIG. 8 illustrates non-encoded bursts 106 and 108, and Applicant'sencoded servo bursts 806 and 808. Applicant's servo bursts 806 and 808,in combination, encode information having a value of “1”. Referring nowto FIG. 8, servo burst 806 comprises pulse 11, pulse 12, pulse 13, andpulse 14. Servo burst 808 comprises pulse 15, pulse 16, pulse 17, andpulse 18.

Pulse 11 of burst 806 comprises a first magnetic phase shift 850, asecond magnetic phase shift 852, and a width w11′ between phase shifts850 and 852. Pulse 12 of burst 806 comprises a third magnetic phaseshift 854, a fourth magnetic phase shift 856, and a width w12′ betweenphase shifts 854 and 856. A separation t11′ separates first magneticphase shift 850 and third magnetic phase shift 854. A separation s11′separates second magnetic phase shift 852 and third magnetic phase shift854.

Pulse 13 of burst 806 comprises a fifth magnetic phase shift 858, asixth magnetic phase shift 860, and a width w13′ between phase shifts858 and 860. A separation t12′ separates third magnetic phase shift 854and fifth magnetic phase shift 858. A separation s12′ separates fourthmagnetic phase shift 856 and fifth magnetic phase shift 858.

Pulse 14 of burst 806 comprises a seventh magnetic phase shift 862, aneighth magnetic phase shift 864, and a width w14′ between phase shifts862 and 864. A separation t13′ separates fifth magnetic phase shift 858and seventh magnetic phase shift 862. A separation s13′ separates sixthmagnetic phase shift 860 and seventh magnetic phase shift 862. Pulse 15of burst 808 comprises a ninth magnetic phase shift 866, a tenthmagnetic phase shift 868, and a width w15′ between phase shifts 866 and868. Pulse 16 of burst 808 comprises an eleventh magnetic phase shift870, a twelfth magnetic phase shift 872, and a width w16′ between phaseshifts 870 and 872. A separation t15′ separates ninth magnetic phaseshift 866 and eleventh magnetic phase shift 870. A separation s15′separates tenth magnetic phase shift 868 and eleventh magnetic phaseshift 870.

Pulse 17 of burst 808 comprises a thirteenth magnetic phase shift 874, afourteenth magnetic phase shift 876, and a width w17′ between phaseshifts 874 and 876. A separation t16′ separates eleventh magnetic phaseshift 870 and thirteenth magnetic phase shift 874. A separation s16′separates twelfth magnetic phase shift 872 and thirteenth magnetic phaseshift 874.

Pulse 18 of burst 808 comprises a fifteenth magnetic phase shift 878, asixteenth magnetic phase shift 880, and a width w18′ between phaseshifts 878 and 880. A separation t17′ separates thirteenth magneticphase shift 874 and fifteenth magnetic phase shift 878. A separations17′ separates fourteenth magnetic phase shift 876 and fifteenthmagnetic phase shift 878.

In the illustrated embodiment of FIG. 8, for bursts 806 and 808,w11′=w14′=w15′=w18′, and w12′=w13′=w16′=w17′. In certain embodiments,for bursts 806 and 808, w11′=w14′=w15′=w18′=2.0 microns. In certainembodiments, for bursts 806 and 808, w12′=w13′=w16′=w17′=2.25 microns.

In the illustrated embodiment of FIG. 8, for bursts 806 and 808,t11′=t15′, and t12′=t16′, and t13′=t17′. In certain embodiments, forbursts 806 and 808, t11′=t15′=4.75 microns. In certain embodiments, forbursts 806 and 808, t12′=t16′=5.5 microns. In certain embodiments, forbursts 806 and 808, t13′=t17′=5.0 microns.

In the illustrated embodiment of FIG. 8, for bursts 806 and 808,s11′=t13′=s15′=s17′, and s12′=s16′. In certain embodiments, for bursts806 and 808, s11′=s13′=s15′=s17′=2.75 microns. In certain embodiments,for bursts 806 and 808, s12′=s16′=3.0 microns.

FIG. 9 illustrates non-encoded bursts 106 and 108, and Applicant'sencoded servo bursts 906 and 908. Applicant's servo bursts 906 and 908,in combination, encode information having a value of “0”. Referring nowto FIG. 9, servo burst 906 comprises pulse 11, pulse 12, pulse 13, andpulse 14. Servo burst 908 comprises pulse 15, pulse 16, pulse 17, andpulse 18.

Pulse 11 of burst 906 comprises a first magnetic phase shift 950, asecond magnetic phase shift 952, and a width w11′ between phase shifts950 and 952. Pulse 12 of burst 906 comprises a third magnetic phaseshift 954, a fourth magnetic phase shift 956, and a width w12′ betweenphase shifts 954 and 956. A separation t11′ separates first magneticphase shift 950 and third magnetic phase shift 954. A separation s11′separates second magnetic phase shift 952 and third magnetic phase shift954.

Pulse 13 of burst 906 comprises a fifth magnetic phase shift 958, asixth magnetic phase shift 960, and a width w13′ between phase shifts958 and 960. A separation t12′ separates third magnetic phase shift 954and fifth magnetic phase shift 958. A separation s12′ separates fourthmagnetic phase shift 956 and fifth magnetic phase shift 958.

Pulse 14 of burst 906 comprises a seventh magnetic phase shift 962, aneighth magnetic phase shift 964, and a width w14′ between phase shifts962 and 964. A separation t13′ separates fifth magnetic phase shift 958and seventh magnetic phase shift 962. A separation s13′ separates sixthmagnetic phase shift 960 and seventh magnetic phase shift 962.

Pulse 15 of burst 908 comprises a ninth magnetic phase shift 966, atenth magnetic phase shift 968, and a width w15′ between phase shifts966 and 968. Pulse 16 of burst 908 comprises an eleventh magnetic phaseshift 970, a twelfth magnetic phase shift 972, and a width w16′ betweenphase shifts 970 and 972. A separation t15′ separates ninth magneticphase shift 966 and eleventh magnetic phase shift 970. A separation s15′separates tenth magnetic phase shift 968 and eleventh magnetic phaseshift 970.

Pulse 17 of burst 908 comprises a thirteenth magnetic phase shift 974, afourteenth magnetic phase shift 976, and a width w17′ between phaseshifts 974 and 976. A separation t16′ separates eleventh magnetic phaseshift 970 and thirteenth magnetic phase shift 974. A separation s16′separates twelfth magnetic phase shift 972 and thirteenth magnetic phaseshift 974.

Pulse 18 of burst 908 comprises a fifteenth magnetic phase shift 978, asixteenth magnetic phase shift 980, and a width w18′ between phaseshifts 978 and 980. A separation t17′ separates thirteenth magneticphase shift 974 and fifteenth magnetic phase shift 978. A separations17′ separates fourteenth magnetic phase shift 976 and fifteenthmagnetic phase shift 978.

In the illustrated embodiment of FIG. 9, for bursts 906 and 908,w11′=w12′=w13′=w14′=w15′=w16′=w17′=w18′. In certain embodiments, forbursts 906 and 908, w11′=w12′=w13′=w14′=w15′=w16′=w17′=w18′=2.0 microns.

In the illustrated embodiment of FIG. 9, for bursts 806 and 808,t11′=t13′=t15′=t17′, and t12′=t16′. In certain embodiments, for bursts906 and 908, t11′=t13′=t15′=t17′=4.75 microns. In certain embodiments,for bursts 806 and 808, t12′=t16′=5.5 microns.

In the illustrated embodiment of FIG. 9, for bursts 906 and 908,s11′=s13′=s15′=s17′, and s12′=s16′. In certain embodiments, for bursts806 and 808, s11′=s13′=s15′=s17′=2.75 microns. In certain embodiments,for bursts 806 and 808, s12′=s16′=3.5 microns.

Table 1 summarizes the information that can be encoded in each 4 burstservo pattern using prior art methods.

TABLE 1 PRIOR ART SUBFRAME 1 SUBFRAME 2 ENCODED INFORMATION 102, 104106, 108 NONE 202, 204 106, 108 1 302, 304 106, 108 0

Using an unencoded Subframe 1 architecture described hereinabove incombination with Applicants' Subframe 2 architecture, Applicant's methodcan encode 1 bit of information in each servo pattern written to asequential storage medium. Table 2 summarizes the information that canbe encoded in each four burst servo pattern using this embodiment ofApplicant's method.

TABLE 2 ENCODING 1 BIT PER SERVO PATTERN SUBFRAME 1 SUBFRAME 2 ENCODEDINFORMATION 102, 104 806, 808 1 102, 104 906, 908 0

Using Applicant's Subframe 1 architecture described hereinabove incombination with the prior art Subframe 2 architecture, Applicant'smethod can encode 2 bits of information in each servo pattern written toa sequential storage medium. Table 3 summarizes the information that canbe encoded in each four burst servo pattern using this embodiment ofApplicant's method.

TABLE 3 ENCODING 2 BITS PER SERVO PATTERN SUBFRAME 1 SUBFRAME 2 ENCODEDINFORMATION 402A, 404A 106, 108 10 402B, 402B 106, 108 10 502A, 504A106, 108 11 502B, 504B 106, 108 11 602, 604 106, 108 00 702A, 704A 106,108 01 702B, 704B 106, 108 01

Using Applicant's Subframe 1 architecture described hereinabove incombination with Applicant's Subframe 2 architecture describedhereinabove, Applicant's method can encode 3 bits of information in eachservo pattern written to a sequential storage medium. Table 4 summarizesthe information that can be encoded in each 4 burst servo pattern usingthis embodiment of Applicant's method.

TABLE 4 ENCODING 3 BITS PER SERVO PATTERN SUBFRAME 1 SUBFRAME 2 ENCODEDINFORMATION 402A, 404A 806, 808 101 402B, 404B 806, 808 101 502A, 504A806, 808 111 502B, 504B 806, 808 111 602, 604 806, 808 001 702A, 704A806, 808 011 702B, 704B 806, 808 011 402A, 404A 906, 908 100 402B, 404B906, 908 100 502A, 504A 906, 908 110 502B, 504B 906, 908 110 602, 604906, 908 000 702A, 704A 906, 908 010 702B, 704B 906, 908 010

In certain embodiments, Applicant's sequential information storagemedium comprises a plurality of servo patterns encoded sequentiallyalong its length. In certain embodiments, Applicant's method aggregatesthe information encoded in a sequential plurality of servo patterns toform one or more words. In certain embodiments, Applicant's methodaggregates the information encoded in 36 sequential servo patterns toform three words, wherein the information encoded in four sequentialservo patterns comprises manufacturer information, and wherein theinformation encoded in eight sequential servo patterns comprises syncinformation, and wherein the information encoded in twenty-four (24)sequential servo patterns comprises LPOS information. Using the priorart servo patterns of Table 1, the four sequential servo patterns whichin combination are used to encode manufacturer information comprise, inthe aggregate, 4 bits of information. Using Applicant's servo patternsof Table 2, the four sequential servo patterns which in combination areused to encode manufacturer information comprise, in the aggregate, 8bits of information. As those skilled in the art will appreciate, use ofApplicant's servo patterns of Table 2 allows the encoding of two timesthe amount of manufacturer information as does use of prior art servopatterns. As those skilled in the art will further appreciate, use ofApplicant's servo patterns of Table 2 allows a higher reliability in thedecoding of manufacturer information as compared to the use of prior artservo patterns.

Using Applicant's servo patterns of Table 3, the four sequential servopatterns which in combination are used to encode manufacturerinformation comprise, in the aggregate, 12 bits of information. As thoseskilled in the art will appreciate, use of Applicant's servo patterns ofTable 3 allows the encoding of three times the amount of manufacturerinformation as does use of prior art servo patterns. As those skilled inthe art will appreciate, use of Applicant's servo patterns of Table 3allows a higher reliability in the decoding of manufacturer informationas compared to the use of prior art servo patterns.

Using the prior art servo patterns of Table 1, the eight sequentialservo patterns which in combination are used to encode sync informationcomprise, in the aggregate, 8 bits of information. Using Applicant'sservo patterns of Table 2, the eight sequential servo patterns which incombination are used to encode sync information comprise, in theaggregate, 16 bits. As those skilled in the art will appreciate, use ofApplicant's servo patterns of Table 2 allows the encoding of two timesthe amount of sync information as does use of prior art servo patterns.As those skilled in the art will further appreciate, use of Applicant'sservo patterns of Table 3 allows the encoding of three times the amountof sync information as does use of prior art servo patterns.

Using the prior art servo patterns of Table 1, the 24 sequential servopatterns which in combination are used to encode LPOS informationcomprise, in the aggregate, 24 bits of information. Using Applicant'sservo patterns of Table 2, Applicant's sequential 24 servo patterns usedto encode LPOS information comprise, in the aggregate, 48 bits ofinformation. Using Applicant's servo patterns of Table 3, Applicant'ssequential 24 servo patterns used to encode LPOS information comprise,in the aggregate, 72 bits of information. As those skilled in the artwill appreciate, use of Applicant's servo patterns of Table 2 or Table 3allows a higher reliability in the decoding of LPOS information ascompared to the use of prior art servo patterns.

Applicant's invention further comprises an article of manufacture, suchas and without limitation a tape drive apparatus, a data storagecontroller, an automated data storage library, a host computing devicecomprising a storage management program and in communication with a datastorage library, wherein that article of manufacture comprises acomputer readable medium comprising computer readable program codecomprising a series of computer readable program steps to effectencoding a plurality of Applicant's servo patterns in one or morenon-data regions of a sequential information storage medium, and/ordecoding information encoded in a plurality of Applicant's servopatterns of Table 2 and/or Table 3.

Applicant's invention further includes a computer program productencoded in a computer readable medium and usable with a computerprocessor to encode a plurality of Applicant's servo patterns in one ormore non-data regions of a sequential information storage medium, and/ordecode information encoded in a plurality of Applicant's servo patternsof Table 2 and/or Table 3.

While the preferred embodiments of the present invention have beenillustrated in detail, it should be apparent that modifications andadaptations to those embodiments may occur to one skilled in the artwithout departing from the scope of the present invention as set forthin the following claims.

1. A sequential data storage medium, comprising a sequence of aplurality of servo patterns encoded in a non-data region, wherein eachof said servo patterns comprises: a first burst pattern comprising afirst pulse comprising a first width, a second pulse comprising a secondwidth, a third pulse comprising a third width, a fourth pulse comprisinga fourth width, and a fifth pulse comprising a fifth width; a secondburst pattern comprising a sixth pulse comprising a sixth width, aseventh pulse comprising a seventh width, an eighth pulse comprising aneighth width, a ninth pulse comprising a ninth width and a tenth pulsecomprising a ten width; a third burst pattern comprising an eleventhpulse comprising an eleventh width, a twelfth pulse comprising a twelfthwidth, a thirteenth pulse comprising a thirteenth width, and afourteenth pulse comprising a fourteenth width; a fourth burst patterncomprising a fifteenth pulse comprising a fifteenth width, a sixteenthpulse comprising a sixteenth width, a seventeenth pulse comprising aseventeenth width, and an eighteenth pulse comprising an eighteenthwidth; wherein widths of said plurality of pulses which comprise saidfirst burst pattern and said second burst pattern, in combination withspacings between said plurality of pulses comprising said first burstpattern and said second burst pattern, encode two bits of data; andwherein widths of said plurality of pulses which comprise said thirdburst pattern and said fourth burst pattern, in combination withspacings between said plurality of pulses comprising said third burstpattern and said fourth burst pattern, encode one bit of data; wherein:said eleventh width equals said fourteenth width; said twelfth widthequals said thirteenth width; said twelfth width is greater than saideleventh width; said third burst pattern and said fourth burst patternencode a value of “1”.
 2. The sequential data storage medium of claim 1,wherein: said eleventh width, and said twelfth width, and saidthirteenth width, and said fourteenth width, are equal; said third burstpattern and said fourth burst pattern encode a value of “0”.
 3. A methodto encode linear position information in a sequential data storagemedium, comprising the steps of: encoding (N) sequential servo patternsalong a portion of said sequential data storage medium, wherein (N) isgreater than 1; wherein the encoding step for each of said (N) LPOSservo patterns comprises the steps of: encoding a first burst patterncomprising a first plurality of pulses; encoding a second burst patterncomprising a second plurality of pulses; encoding a third burst patterncomprising a third plurality of pulses; encoding a fourth burst patterncomprising a fourth plurality of pulses; wherein widths of saidplurality of pulses which comprise said first burst pattern and saidsecond burst pattern, in combination with spacings between saidplurality of pulses which comprise said first burst pattern and saidsecond burst pattern, encode two LPOS bits.
 4. The method of claim 3,wherein: said first pulse comprises a first magnetic phase shift and asecond magnetic phase shift; said second pulse comprises a thirdmagnetic phase shift and a fourth magnetic phase shift; said third pulsecomprises a fifth magnetic phase shift and a sixth magnetic phase shift;said fourth pulse comprises a seventh magnetic phase shift and an eighthmagnetic phase shift; said fifth pulse comprises a ninth magnetic phaseshift and a tenth magnetic phase shift; said sixth pulse comprises aneleventh magnetic phase shift and a twelfth magnetic phase shift; saidseventh pulse comprises a thirteenth magnetic phase shift and afourteenth magnetic phase shift; said eighth pulse comprises a fifteenthmagnetic phase shift and a sixteenth magnetic phase shift; said ninthpulse comprises a seventeenth magnetic phase shift and an eighteenthmagnetic phase shift; and said tenth pulse comprises a nineteenthmagnetic phase shift and a twentieth magnetic phase shift; said firstmagnetic phase shift and said third phase shift are separated by a firstseparation; said third magnetic phase shift and said fifth phase shiftare separated by a second separation; said fifth magnetic phase shiftand said seventh phase shift are separated by a third separation; saidseventh magnetic phase shift and said ninth phase shift are separated bya fourth separation; said eleventh magnetic phase shift and saidthirteenth phase shift are separated by a sixth separation; saidthirteenth magnetic phase shift and said fifteenth phase shift areseparated by a seventh separation; said fifteenth magnetic phase shiftand said seventeenth phase shift are separated by a eighth separation;said seventeenth magnetic phase shift and said nineteenth phase shiftare separated by an ninth separation; wherein for a first servo pattern:said first separation, said third separation, said sixth separation, andsaid eighth separation, equal 4.75 microns; said second separation, saidfourth separation, said seventh separation, and said ninth separation,equal 5.25 microns; said first servo pattern encodes a value “10”. 5.The method of claim 4, wherein for a second servo pattern: said firstseparation, said second separation, said sixth separation, and saidseventh separation, equal 5.0 microns; said third separation, and saideighth separation, equal 4.5 microns; and said fourth separation andsaid ninth separation, equal 5.5 microns; said second servo patternencodes a value “01”.
 6. The method of claim 4, wherein for a thirdservo pattern: said first separation, said fourth separation, said sixthseparation, and said ninth separation, are equal in length to 4.75microns; said second separation, said third separation, said seventhseparation, and said eighth separation, are equal in length to 5.25microns; and said second servo pattern encodes a value “11”.
 7. Themethod of claim 4, wherein for a fourth servo pattern: said firstseparation, said fourth separation, said sixth separation, and saidninth separation, are equal in length to 5.25 microns; said secondseparation, said third separation, said seventh separation, and saideighth separation, are equal in length to 4.75 microns; and said secondservo pattern encodes a value “00”.
 8. The method of claim 3, wherein:said third burst pattern comprises an eleventh pulse, a twelfth pulse, athirteenth pulse, and a fourteenth pulse; said fourth burst patterncomprises a fifteenth pulse, a sixteenth pulse, a seventeenth pulse, andan eighteenth pulse; wherein the widths of said plurality of pulsescomprising said third burst pattern and said fourth burst pattern, incombination with the spacings between said plurality of pulsescomprising said third burst pattern and said fourth burst pattern,encode one LPOS bit.
 9. The method of claim 8, wherein: said eleventhpulse comprises a first width; said twelfth pulse comprises a secondwidth; said thirteenth pulse comprises said second width; saidfourteenth pulse comprises said first width; said second width isgreater than said first width; said third burst pattern and said fourthburst pattern encode a value of “1”.
 10. The method of claim 8, wherein:said eleventh pulse comprises a first width; said twelfth pulsecomprises said first width; said thirteenth pulse comprises said firstwidth; said fourteenth pulse comprises said first width; said thirdburst pattern and said fourth burst pattern encode a value of “0”.